Nitroxide polymer brushes grafted on silica nanoparticles as binder-free cathode for organic radical battery have been investigated. Scanning electron microscopy, transmission electron microscopy, infrared spectroscopy and electron spin resonance confirm that the nitroxide polymer brushes are successfully grafted onto silica nanoparticles via surface-initiated atom transfer radical polymerization. The thermogravimetric analysis results indicate that the onset decomposition temperature of these nitroxide polymer brushes is found to be ca. 201 ◦C. The grafting density of the nitroxide polymer brushes grafted on silica nanoparticles is 0.74¡V1.01 chains nm−2. The results of the electrochemical quartz crystal microbalance indicate that the non-crosslinking nitroxide polymer brushes prevent the polymer from dissolving into organic electrolytes. Furthermore, the electrochemical results show that the discharge capacity of the polymer brushes is 84.9¡V111.1 mAh g−1 at 10 C and the cells with the nitroxide polymer brush electrodes have a very good cycle-life performance of 96.3% retention after 300 cycles.

Exploitation of well defined responsive polymer brushes for direct and controlled immobilization of metal/semiconductor nanoparticles on macroscopic surfaces has been demonstrated. The employed approach offers the possibility of the organization of a variety of inorganic nanoparticles by irreversible bonding and homogenous distribution on an underlying substrate. The immobilization process has been realized by chemical grafting of a variety of polymer brushes on a suitable substrate followed by the attachment of pre-/in-situ formed nanoparticles exploiting the chemical/physical interactions between surface functionalities of nanoparticles and polymer chain segments. A number of polymer brushes including poly (acrylic acid), polystyrene, poly (2-vinyl pyridine) and poly (N-isopropyl acrylamide) brushes have been prepared on silicon substrate by the “grafting to” approach. A variety of inorganic nanoparticles such as quantum dots (CdTe) noble metals (gold and silver) and magnetic (Fe3O4) were immobilized on macroscopic surfaces to impart them photo luminescent, catalytic or magnetic properties. In addition, responsiveness of grafted polymer brushes in terms of variation in thickness (due to changes in chain conformation) as a function of external stimuli such as solvent and pH allowed to use the resulting polymer brush-nanoparticles nanoassemblies in the fabrication of nanosensors. The design of fabricated nanosensors is based on the modulation in the interparticle distance of immobilized nanoparticles due to swelling/deswelling of underlined polymer brushes in response to some external trigger.

Orientador: Marcos David Ferreira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola / Made available in DSpace on 2018-08-10T16:46:51Z (GMT). No. of bitstreams: 1 Magalhaes_AnaMariade_M.pdf: 1240631 bytes, checksum: 4a79b5e3d3142664212a05d902d6fc6b (MD5) Previous issue date: 2007 / Resumo: A etapa de limpeza em uma linha de beneficiamento para tomate de mesa é importante, pois é responsável pela retirada de impurezas externas dos frutos, sem danificálos. O objetivo deste trabalho foi avaliar a eficácia da limpeza e a qualidade dos frutos após serem submetidos a esse processo, alterando o tipo de cerdas e as rotações das escovas utilizadas, tendo como modelo referencial o tomate de mesa Débora. Os ensaios foram realizados em laboratório, na etapa de limpeza do protótipo UNIMAC1. Primeiramente, identificou-se entre as metodologias, análise com colorímetro e turbidímetro, a mais adequada para avaliar a eficácia de limpeza. Para isto utilizou-se esferas de borracha, de peso similar ao tomate, que foram sujas artificialmente e passaram pela limpeza no protótipo com cerdas de nylon e rotação de 100 rpm. Em uma segunda etapa, avaliou-se a eficácia de limpeza, utilizando as esferas de borracha, variando-se o tipo de cerda (nylon, sisal, Tereftalato de polietileno - PET e fibra de coco) e a rotação (40, 80, 120 e 160 rpm) das escovas. E por fim, realizou-se o estudo com o tomate de mesa, analisando a eficácia da limpeza e a qualidade dos frutos (perda de massa, atividade respiratória, concentração de etileno e aparência externa). Observou-se que a análise com o turbidímetro foi a mais precisa na avaliação da eficácia de limpeza. No ensaio com as esferas, o uso de cerdas mais flexíveis, nylon e sisal, que apresentam um índice de flexibilidade (Gc) de 68,34 e 70,27 N.m-1, respectivamente, combinadas a altas rotações tornaram o processo de limpeza mais eficaz. A cerda PET, que é mais rígida, Gc de 135,94 N.m-1, e a rotação de 40 rpm foram ineficientes, apresentando um índice de limpeza inferior a 50%. Para os frutos de tomate, o tratamento cerdas de nylon a 120 rpm foi o mais eficaz no processo de limpeza, com um índice de limpeza de 91%, já na rotação de 160 rpm o índice foi inferior (88%), uma vez que devido à alta velocidade das escovas os frutos pulavam e assim não eram envoltos pelas cerdas. Os menores índices de limpeza, 75,4 e 78,8% foram obtidos nos tratamentos com fibra de coco a 80 e a 120 rpm, respectivamente. De um modo geral, os frutos limpos apresentaram alta perda de massa, alta atividade respiratória e um maior incremento na concentração de etileno após o processo de limpeza. A limpeza dos frutos não foi perceptível na análise sensorial, todavia os tomates que passaram pela limpeza foram os mais aceitos no teste de intenção de compra. Assim concluiuse que a cerda de nylon, por ser mais flexível, quando combinada à rotação de 120 rpm, envolveu melhor os frutos, tornando a limpeza mais eficaz. Contudo, tal processo aumentou a perda de massa e a atividade respiratória logo após o tratamento. Por outro lado quando combinada à rotação de 160 rpm, apesar do processo ser mais ineficiente com relação à limpeza, ocorreu menores alterações de qualidade nos frutos / Abstract: The cleaning step of a packing line for fresh tomatoes is very important, because it is responsible for removing surface residues of fruits without injuring. The main goal of this work was to evaluate cleaning efficiency and fruit quality submitted to different types of bristles and rotations, having as referential model the fresh market tomato Débora. The assays were carried out in a laboratory, in a cleaning step on a prototype developed and named UNIMAC1. First, an assay was carried out to identify the best method for evaluating cleaning efficiency: colorimeter or turbidimeter. Then, rubber spheres, with similar tomato weight, were artificially dirtied and submitted to the cleaning step on the prototype, with brushes of nylon bristles and rotation of 100 rpm. Afterwards, in a second process, the efficiency cleaning was evaluated and the rubber spheres were used again, changing the types of bristles (nylon, sisal fiber, PET and coconut fiber) as well as the rotation (40, 80, 120 and 160 rpm) of rotary brushes. The last phase, the studies were carried out with fresh tomatoes for evaluating cleaning efficiency and fruit quality (weight loss, respiratory rate, ethylene evolution and external appearance). Results showed that the turbidimeter method was the most accurate methodology for evaluating cleaning efficiency. On the trials where rubber spheres were used, the flexible bristles, nylon and sisal fiber, which demonstrated a flexible index (Gc) of 68.34 and 70.27 N.m-1, respectively, were more efficient at higher rotations. PET bristles, that are stiffer (Gc of 135.94 N.m-1) and at a rotation of 40 rpm, were inefficient, presenting a cleaning index lower than 50%. For the fresh tomatoes, a nylon brush at 120 rpm treatment was the most efficient cleaning process, showing a cleaning index of 91%. Nylon brushes at 160 rpm treatment showed the lowest cleaning index (88%). These results were probably associated to the fact that, at higher speeds, fruits tended to jump, causing a poor contact between bristles and fruits. The lowest cleaning index, 75.4 and 78.8%, were observed on coconut fiber at 80 and 120 rpm treatments, respectively. In general, cleaned fruits demonstrated high weight loss, high respiratory rate and more evolution of ethylene after cleaning process. Cleaning efficiency of fruits was not perceptible in sensory analysis; however tomatoes that were submitted to cleaning were more accepted by the buy intention test, being the clean fruits in coconut fiber at 80 rpm treatment preferred by buyers. In conclusion, as nylon bristles are more flexible, allowing a more intimate contact with fruits at 120 rpm, the cleaning process for these parameters is more efficient. However this treatment increased weight loss and respiratory rate after cleaning. On the other hand, nylon at 160 rpm treatment showed to be more inefficient in relation to cleaning, but showed fewer fruits alterations / Mestrado / Tecnologia Pós-Colheita / Mestre em Engenharia Agrícola

Polymer brushes can be used to tailor the physical and chemical properties of materials on demand to meet potential applications. Therefore, fabrication of polymer brushes with well-defined structure and functional groups enables the engineering of new materials with diverse functions. In addition, two-dimensional (2D) materials have their unique physical/chemical properties and potential applications in (opt)electronics, catalysis, energy storage, sensing, and other related fields. However, the dispersibility, chemical stability, charge transport behavior, mechanical properties of the 2D materials hinder their further applications. Therefore, combining polymer brushes and 2D materials may bring in new properties which are not available by either of them alone. This thesis focuses on brushing up 2D materials (from inorganic to organic) with universal photografting techniques. (1) The first chapter introduces the outline and research content of the thesis. (2) The second chapter describes the background of 2D materials and polymer brushes. In particular, this chapter analyzes mechanisms, drawbacks and benefits of different polymerization methods, and also summarizes the general approaches to grow polymer brushes on 2D material surfaces, coupling with potential applications of polymer functionalized 2D materials. (3) The third chapter shows the motivation and aim of this thesis. (4) The fourth chapter discusses the results of the functionalization of hexagonal boron nitride (hBN), MoS2, graphitic-carbon nitride (gCN), alkyl-polydopamine (alkyl-PDA), and conjugated 2D polymers (2DPs) with polymer brushes by the same self-initiated photografting and photopolymerization (SIPGP) method and their related applications in detail, respectively. First, the direct photopolymerization of vinyl monomers results in the formation of thick and homogeneous polymer brushes covalently bounded to hBN. The brush layer mechanically and chemically stabilizes the material and allows facile handling as well as long-term use in water splitting hydrogen evolution reactions. Second, the chapter demonstrates the MoS2 can be directly modified with polymer brushes by SIPGP. After modifying MoS2 with polymer brushes, the dispersibility of polymer brushes-modified MoS2 was obviously improved. Third, the polymer brushes functionalized gCN significantly improves the dispersibility. Application of polymer brush functionalized gCN as excellent recyclable substrates for an outstanding SERS as well as photocatalytic degradation of dyes is demonstrated. Fourth, to directly obtain the 2D materials with functional groups, the chapter proposes a facile method to prepare amphiphilic polymeric Janus nanosheets with hydrophilic PDA and hydrophobic alkyl chains at both sides. Benefiting from the Janus property of the alkyl-PDA nanosheets, the nanosheets can be grafted polymer brushes through photografting and be conjugated Fe3O4 nanoparticles selectively onto the PDA side. Finally, the chapter shows that various polymer brushes can be directly grafted onto 2DPs and freestanding system is also obtained. Moreover, it is found that the morphology of freestanding system quickly and reversibly responds to solvent quality by shrinking/stretching. (5) The fifth chapter addresses the general conclusion and future prospective of the whole work. (6) The sixth chapter describes the experiment part of the whole thesis.

Title: Bioactive interfaces between synthetic surfaces and biological fluids Author: Andrés de los Santos Pereira Institute: Institute of Macromolecular Chemistry, Czech Academy of Sciences Supervisor of the doctoral thesis: RNDr. Eduard Brynda, CSc., Institute of Macromolecular Chemistry, Czech Academy of Sciences Abstract: The application in medicine of label-free affinity biosensors, advanced implants, and blood-contacting devices requires that their surfaces resist non-specific protein adsorption (fouling) and associated complications in blood-derived fluids while displaying immobilized bioreceptors that provide specific biofunctionality. The aim of this thesis was to explore the strategies for the preparation of these antifouling bioactive surfaces. Various types of recently developed antifouling polymer brushes were synthesized and evaluated in terms of their ability to prevent fouling from blood plasma (obtained from various commercial sources and individual donors) as well as thrombus formation when contacted with whole blood. Moreover, single-cell force spectroscopy was utilized to characterize the bacterial adhesion force and energy on these polymer brushes, which were significantly reduced in comparison to various reference substrates. The immobilization of bioreceptors was tackled by means of a...

Exploitation of well defined responsive polymer brushes for direct and controlled immobilization of metal/semiconductor nanoparticles on macroscopic surfaces has been demonstrated. The employed approach offers the possibility of the organization of a variety of inorganic nanoparticles by irreversible bonding and homogenous distribution on an underlying substrate. The immobilization process has been realized by chemical grafting of a variety of polymer brushes on a suitable substrate followed by the attachment of pre-/in-situ formed nanoparticles exploiting the chemical/physical interactions between surface functionalities of nanoparticles and polymer chain segments. A number of polymer brushes including poly (acrylic acid), polystyrene, poly (2-vinyl pyridine) and poly (N-isopropyl acrylamide) brushes have been prepared on silicon substrate by the “grafting to” approach. A variety of inorganic nanoparticles such as quantum dots (CdTe) noble metals (gold and silver) and magnetic (Fe3O4) were immobilized on macroscopic surfaces to impart them photo luminescent, catalytic or magnetic properties. In addition, responsiveness of grafted polymer brushes in terms of variation in thickness (due to changes in chain conformation) as a function of external stimuli such as solvent and pH allowed to use the resulting polymer brush-nanoparticles nanoassemblies in the fabrication of nanosensors. The design of fabricated nanosensors is based on the modulation in the interparticle distance of immobilized nanoparticles due to swelling/deswelling of underlined polymer brushes in response to some external trigger.

Detta examensarbete handlar om att ta fram ett koncept på alternativa borstar och en bottenplåt i alternativt material för Weda W50. Anledningen till detta är att dagens borstar kräver ständig och noggrann rengöring för att inte haverera samt att bottenplåten orsakar elektrolytisk korrosion på resterande komponenter. För att kunna uppnå godtagbara resultat har metoder som idégenerering, materialsökning, modellering samt prototypframtagning använts. I genomförandefasen har tester utförts för att få en demonstration på hur de slutgiltiga komponenterna kommer att fungera i praktiken. Efter en avslutad genomförandefas blev resultatet fasta borstar med omdesignade länkarmar samt en bottenplåt i ABS-plast, vilket presenterats med både 3D-modellering och i fysisk komponent. Därmed har målen och syftet med detta examensarbete uppfyllts. / The purpose of this thesis is to examine and generate alternative concepts for the pool brushes and bottom plates used in the W50 underwater cleaning robot. The reason is that the current rotating brushes used on the W50 require thorough and consistent servicing to function as advertised, the other cause is that the bottom plate is produced in stainless steel which causes electrolytic corrosion on the surfaces of other components that are made in aluminum. Brainstorming, material research, 3D-modeling and prototyping were used to achieve tangible results. Several tests were conducted during the execution phase to give a live demonstration of how the final product is meant to perform. The results of the execution phase became fixed brushes for the W50, redesigned control arms and a bottom plate in ABS plastic. The results of this thesis work were demonstrated with the help of both 3D-modeling and physical models. Finally, the goals and purposes of this thesis were achieved.

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Surface engineering of tailored materials with adjustable characteristics in relation to biological environment, is one of the main prerequisites for biotechnological applications. In recent years, advanced surface coatings in the nanometer range have drawn big attention. A special category of this group are stimuli responsive polymers tethered by one functional end to the surface. When the surface grafting density is big enough, the polymer chains are forced to stretch away from the interface due to excluded volume effects, creating a so called polymer brush. Nano-scaled polymer brushes are advantageous due to their nanostructure, which can be comparable to biological species, and their collaborative response to external stimuli. Moreover, the material design parameters such as chemistry, surface topography, charge, and surface wettability can be adjusted by using the appropriate polymer, or a combination of polymers with respect to the desired material performance. In case of binary polymer brushes, the materials' properties are switched between the properties of two constituent polymers. Besides, upon switching of external stimuli, biomodified binary polymer brushes can hide or expose biofunctionalities, on demand. Hence, they are classified as smart biomaterials' surface coatings.